Even if you hard forked Bitcoin and modified the code, the actual Bitcoin genesis block wouldn't be spendable. You could be able to spend the genesis block on the new blockchain, but that wouldn't be the genuine Bitcoin genesis block.

When you want to search for more technical aspects of Bitcoin don't use the fucking google (they are hiding results about Bitcoin).

Go directly to:

Here is the answer for your question: https://bitcoin.stackexchange.com/questions/76831/is-the-transaction-within-genesis-block-spendable